1. Field of the Invention
The present invention relates to replaceable-blade utility knives, such as used in the construction trades for cutting sheet materials by hand.
2. Description of Related Art
Hand-held utility knives that have a thin cutting blade with at least one razor-like edge are ubiquitous tools found in the toolbox of almost every tradesman and do-it-yourselfer. These utility knives come in different styles and types, including disposable and reusable types. Reusable types typically include a metallic handle and are generally regarded as stronger and more reliable than disposable, plastic-handled types. Therefore, reusable utility knives are preferred by professionals and serious craftspeople. With disposable knives, the entire knife is discarded when the blade is spent. With reusable knives, only the blade is discarded and replaced with a new blade; hence, such knives may also be referred to as replaceable-blade utility knives.
Replaceable-blade utility knives are generally available in two basic types: retractable-blade knives and fixed-blade knives. Retractable-blade knives, such as knife 90 shown in FIGS. 1A-B, typically use a single-edged blade 92 that is mounted to a sliding blade holder inside of handle 94. The sliding blade holder is connected to a button 96 on the outside of handle 94. By sliding the button 96 along handle 94 to the position shown in FIG. 1B, blade 92 may be retracted into handle 94.
Retractable-blade utility knives are convenient light-duty cutting tools, and their retractable blade enhances their convenience and safety. At the same time, however, the use of a sliding blade holder adds a certain amount of imprecision to the blade mount and weakens the connection between the blade and the handle. For this reason, many professionals and serious craftspeople prefer to use a fixed-blade utility knife for more demanding applications, such as the installation of wall-to-wall carpeting or precision detailed cutting.
As the name implies, in a fixed-blade utility knife, the cutting blade is securely fixed to the handle of the knife. To secure the blade, a thumbscrew or other removable fastener may be used, thereby facilitating convenient replacement of spent blades. But when in use, the blade is securely clamped in place relative to the handle, providing a more trustworthy and precise cutting edge. Consequently, the cutting edge of the blade remains exposed when the knife is not in use, such as when lying in the tool box or carried in a tool pouch. The exposed blade may be covered using a removable safety cover, but such covers are prone to become lost, or may be perceived as inconvenient by some users.
Accordingly, there is a need for a replaceable-blade utility knife that combines the safety and convenience of a retractable-blade knife with the precision and strength of a fixed-blade knife, at an affordable cost.